Electrical conductor



June 28, 1932. I w, ABBOTT I 1,864,512

ELEC TRI CAL CONDUCTOR Filed Sept. 18, 1924 Qvwentoz Char/es W/Zbbo'ff35y: hi4) (M10514 cg 9 Z Patented June 28, 1932 UNITED s'r 'nzs PATENTOFFICE.

CHARLES WILLS ABBOTT, OI ROME, NEW YORK, ASS IGNOR, BY MESNE ASSIGN-'IENTB, '20 GENERAL CABLE CORPORATION, OF NEW YORK, N. Y, A CORPORATIONOF NEW JERSEY ELECTRICAL CONDUCTOR Application filed September 18, 1924.Serial 110'. 788,340.

The resent'invention relates to improvements in insulated electricalconductors or cables which are particularly adapted for use whereexposed-to the weather and other deteriorating influences.

The object ofthe invention is to provide an electrical conductor orcable which will be satisfactorily insulated and suitably constructed towithstand all the efiects of overloading the electrical circuits, whichcannot be easily amaged by fire, water, alkali, salts, abrasion, oil, orimpact and which in other respects will be eminently satisfactor'fi whenused for an apropriate purpose. urther objects 0 the A invention will bein part obvious and in part specifically pointed-out in the followingdescription of a preferred and illustrative embodiment thereof.

It is of prime importance that the wires 39 which are to be used forcertain purposes where exposed shall be well insulated electrically. Itis equally essential that the insulated. conductor or cable formed bythe encasin of wires in rubber compounds or other i electricallyinsulating material be protected against mechanical injury which wouldtend to break down the insulation andpermit short circuits or grounds tooccur. It is desirable that such mechanical increase the electricalprotection afiorded by the usual rubber compound and should be of suchacharacter that it will not be injuriously affected by the tensile andtorsional strains to which the conductors are subjected by bending andby accidental blows or pressure. The conditions under which wires orcables are installed also necessitate the use of a protective coveringwhich will remain substantially unaffected by atmospheric changes andwill not deteriorate when subjected to moisture or water over arelatively lon period of time. For exam le, such con uctors may beinstalled in tlie underbody, wiring of street cars where the material isexposed to a great deal of moisture, to wheel wash, heat, cold oil, andto salts and alkalis, such as are used to keep switch frogs clear of iceduring winter weather. Itis of great importance that the protectivecovering of the insulated wires be highly resistant to fire whether thesame protection should also.

ori 'nates inside theconductor, as by an overloa or outside theconductor, in fact the entire mode of constructing the conductor orcable is directed to minimizing the destructive effects of fire as wellas of water and various corrosive materials.

The conductors or cables constructed and protected in accordance withthe present inventionprovideahomogeneouscompactstructure of materialsall of which have insulating properties. They are of a construction inwhich there are no appreciable air spaces, which is well protectedagainst abrasion, moisture and alkalis which is relatively flexible andwhich will, because of the several 7 compounds with which it isimpregnated, resist the action of any fire that may originate inside oroutside the conductors and which is a relatively poor conductor of heat.

It is contemplated that the present invention may find a principalapplication to electric conductors and cables used in the underbodywiring of street cars, and electric locomotives, on ships, asunderground conductors and the like and I have selected for purposes ofillustration a multi 1e conductor or cable particularly adapted or suchuse. The nature and objects of the invention will be betterunderstoodfrom the following description of such a preferred embodiment.

In the accompanying drawing forming a part hereof,

Figure is a View of a section of cable showing parts progressivelyremoved to show the structure of the cable.

pound 6. The metallic conductors 5 are herev shown as comprising anumber of wires twisted together to form each conductor. The insulatingcompound may be applied to the wires and cured in any suitable mannerand Figure 2 is a cross-sectional View of the preferably has a highpercentage of rubber so that the conductors will be adequately protectedelectrically. 5 v

The conductors covered with the insulating compound are each encased ina helically wound strip of protective material 8 which preferably takesthe form of a strip of insulating fibrous material such as paper whichmay be of laminated construction. The particular form of tape shownconsistsof a strip of relatively thin kraft paper repeatedly folded uponitself until a tape of the required thicknes has been built up. Thisfolding may be accomplished by suitable dies or rollers of such acharacter that a compact tape structure is secured. In thepresentinstance the strip of paper is folded six times. Inasmuch as thisparticular form of tape by itself forms no part of the present inventionit will not be further described herein.

The tape so formed or any other suitable strip-of protective materialmay be carried upon suitable reels or spools in a suitable windingmachine which will carry the reels or spools around the insulated wireas it is drawn along the axis of rotation thereof so that the tape willbe tightly wound onto the wire in the form of a closed helix. In thismanner a very substantial mechanical as well as electrical protection isafforded for the rubber compound.

Preferably a cotton braid 10 is applied over the paper wrapping 8 whichconveniently may be done by leadmg the wrapped conductor to a braidingmachine. The braid is preferably rather open but nevertheless tightlybi'aided upon the paper to hold it securely in p ace.

Inasmuch as the paper tape and cotton braid arenaturallyinfiammabletheyaretreated or impregnated as indicated at 11 to render them fireresisting and at the same time reasonably moisture proof, a treatmentwhich is preferably carried out after the two materials have been placedupon the conductor. The compound may also act as a binder to hold thebraid and tape in place. I prefer to use a fire resisting and moistureproofing compound containing as the principal ingredients zinc oxide andsilicate of soda, with a small percentage of suitable ingredients tohold the same in suspension.

In such a com ound the fire resisting properties are probal fly greaterthan the moisture proofing properties. This compound may be applied inany suitable manner as by leading the braided conductor to an open tankcontaining the compound in suitable condition as to viscosity andtemperature. The compound will penetrate through the open braid l0 andimpregnate to a substantial extent the paper wrapping 8, filling theinterstices thereof. The compound preferably used is such that it willdry quite rapidly so that the conductor may be reeled or taken directlyto the next step in the fabrication of the cable.

In order to distinguish the polarity of individual conductors which arelater made upinto a cable, suitable coloring matter may be added to thecompound and the cable may be made up of individual conductors thusdiffeiently colored and distinguished. The externally presented valleysbetween the individual conductors may be and preferably are filled witha suitable cord 14 of jute or other appropriate material arranged tofill out the valleys so as to provide cable which as a whole issubstantially round in crosssection. These cords are preferably treatedwith the fire proofing compound used in treating the individualinsulated conductors and may be of material so selected as to add to thetensile strength of the cable as a whole.

The individual conductors suitably assem-- bled to form a substantiallyround cable are bound together by a sheath of suitable materialcharacterized by a relatively high tensile strength and insulating valueas well as being substantially impervious to moisture. For this purpose,I have found to be satisfactory a rubberized fibrous material such as astrip of paper containing a rubber compound. This sheath is designed notonly to securely bind the several conductors together but also toprovide a protection against moisture or -abrasion or the effects of anydeleterious substances such as salts and alkalis used in winter weatherto keep switches, frogs and the like from freezing.

In the particular structure shown the sheath consists of a laminatedstrip providing a strip of substantial width and of multiple thicknessto insure strength and imperviousness. It is wound in overlappedrelation, each successive turn overlying substantially onehalf of thewidth of the previous turn so as to provide a continuous sheath which isentirely moisture-proof. It is wound under considerable tension so thatthe overlying half width will compact and usually wrinkle the inner halfwidth of the preceding winding over which it is wound. The character ofthe material is such that there is a substantial adhesion betweensuccessive layers.

The rubberized strip shown consists of rubber impregnated laminatedpaper and in itself is more or less inflammable. For this reason it maybe desirable to apply a-coating of fire proofing or fire resistingmaterial thereto. Such a coating isindicated at 19. The same fireresisting and water proofing compound as used in treating the braid 10and paper 8 may advantageously be used.

Surrounding this rubberized aper there is provided a cord casing, thecord being braided as indicated in Figure 1. As shown three parallelcords are arrangedto form each strand 16 and the several strands arebraided to form a substantially continuous casing 17enclosing the wholecable. This cord jacket is treated with a fire and water proofingcompound as indicated at 18 compounded to afford great resistance tomechanical injury and substantial or complete imperviousness to waterand other destructive liquids which are likely to come into contact withthe cable under the conditions of use for which the cable is moreparticularly designed. The compound particularly selected for use in thepreferred form of cable consists principally of lithopone and baryteswith a relatively small proportion of linseed oil. This com ound ispreferably somewhat thick and o a character to harden to form arelatively hard and tough coating. It is applied to the jacket in amanner to thoroughly impregnate the same and to form on its exterior acoating of substantial thickness whereby it, with the cord jacket formsa relatively hard and tough casing which offers great resistance toabrasion as well as to damage by heat.

The embodiment of the invention described provides a homogeneous compactstructure which is relatively inexpensive to manufacture and yet itsqualities are far superior to those of even more expensive materials now1n common use.

Although only one embodiment of the invention has been shown anddescribed herein it will be understood that the invention may bevariously modified and embodied within the scope of the subjoinedclaims.

I claim:

1. As an article of manufacture an electrical cable comprising incombination, metallic electrical conductors, a surrounding sheath ofrubber insulating compound for each of said conductors, a protectivecovering in strip form-closely wound about each of said insulatedconductors, a fabric jacket surroundin each of said protectivecoverings, arub erized fibrous strip surrounding the several conductorsand bindin the same together, said strip being woun helically inoverlapped relation, one-half of the width of each wrapping overlyingone-half of the width of the preceding wrapping and being wrappedtightly to compress the overlapped portion, and an enclosing casingconsisting of cords arranged in groups and braided together, said casingbeing treated with fire and waterproof material consisting principallyof lithopone and barytes.

2. An electrical cable as defined in claim 1 wherein the rubberizedfibrous strip consists surrounding the several conductors and bindin thesame together, said strip being wound he call in overlapped relation,one-half of the wi th of each wrapping overlying onehalf of the width ofthe preceding wrapping and being wrapped tightly to compress theoverlapped portion, and an enclosing braided casing treated with fireand waterproof material consisting principally of lithopone and barytessubstantially as described.

4. A cable which comprises the combination of an insulated conductor, anarmor enclosing the conductor and made up of a nonmetallic strip woundhelically about the conductor and with the convolutions overlapping.

5. A cable which comprises an insulated conductor, a beddingabout theconductor, an armor on the bedding made up of overlap ing convolutionsof non-metallic tape, an a protective covering over the armor.

6. A cable which comprises the combination of an insulated conductor andan armor enclosing the conductor and made up of a laminated non-metallicstrip wound helically about the conductor with adjacent convolutionsoverlapping.

7. A cable which comprises the combination of a plurality ofindividually insulated conductors and an armor enclosing and binding theseveral conductors together, said armor being made up of a non-metallicstrip wound helically about theassembled conductors with theconvolutions overlapping.

In testimony whereof, I have signed my name to this specification this9th day of September 1924.

dHARLEs WILLS ABBOTT.

ing in stripforin closely woundabout each of said insulated conductors,a fabric jacket surrounding each of said protective coverings, saidjacketed insulated conductors being arranged one centrally and theremaining in a circ e thereabout to rovide a substantially circularcable, a ru berized fibrous strip

